Overcurrent Protection; Overvoltage Protection - Siemens SINAMICS S120 Equipment Manual

Cabinet design and EMC for components, Blocksize format
11.5 24 V DC Supply Voltage
11.5.2

Overcurrent protection

The cables on the primary and secondary sides of the 24 V power supply unit must be
protected against overcurrent.
Primary side protection must be implemented according to the manufacturer's instructions.
Secondary side protection depends on the prevailing situation. Please note the following:
● Loading due to loads, including simultaneity factor depending on machine operation
● Current carrying capacity of the conductors used and cables in normal and short-circuit
conditions
● Ambient temperature
● Cable bundling (routing cables in a common duct)
● Cable routing method according to EN 60204-1
The overcurrent protection devices can be determined according to EN 60204-1.
Circuit-breakers from Siemens Catalogs LV 1 and LV 1T are recommended as overcurrent
protection devices on the primary side.
Miniature circuit-breakers or SITOP select (Article No. 6EP1961-2BA00) are recommended
as overcurrent protection devices on the secondary side. The miniature circuit-breakers can
also be selected from Siemens LV 1 and LV 1T Catalogs.
Miniature circuit-breakers are recommended as overcurrent protection devices for the cables
and busbars. The ground potential M must be connected to the protective conductor system
(PELV/SELV).
When selecting the miniature circuit-breaker, local installation regulations must be carefully
complied with.
Table 11- 1
Conductor cross section
1.5 mm
2.5 mm
4 mm
6 mm
The tripping characteristic of the circuit-breaker is selected so that loads remain protected
against the maximum current that occurs in the event of a short circuit of the power supply
unit.
11.5.3

Overvoltage protection

Surge protection devices are required for cable lengths greater than 30 m.
The following Weidmüller overvoltage protectors are recommended for protecting the
components' 24 V power supply and the 24 V signal cables from overvoltage:
374
MCBs by conductor cross section and temperature
(AWG 16)
2
(AWG 14)
2
(AWG 12)
2
(AWG 10)
2
Max. value up to 40° C
10 A
16 A
25 A
32 A
Max. value up to 55° C
6 A
10 A
16 A
20 A
Manual, 06/2019, 6SL3097-5AL00-0BP1
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